A new assay for serum albumin has been developed based on its enzymatic activity in hydrolyzing a fluorogenic naphthol substrate. The method correlated well with the Bromcresol Green method which is usually used in clinical laboratories. However, the new enzymic fluorescence method is more sensitive, with a limit of detection of 14 picomoles of albumin. A spectra and lifetime atlas is nearly complete for a number of covalently attached fluorescent dyes each as DNS, o-phthalaldehyde, fluorescamine, fluorescein, rhodamine B, eosin, etc. Data have been accumulated for ovalbumin labeled under standard conditions and examined at 23. The spectra were obtained on Aminco-Bowman spectrofluorometers and corrected for instrumental non-linearities. A new method, "fluorescence difference decay" photometry, has been developed. The method is analogous to difference spectroscopy in absorption or fluorescence. When a sample is partly quenched, the decay curve of the quenched sample is subtracted from that of the unquenched sample to give the decay curve for the fluorophor which was quenched. Variations of the method are useful to resolve complex fluorescence decays, which characterize most biological samples. Planning and design for a new YAG-laser based single-photon lifetime apparatus has been in progress. Computer support has been updated. The system components will have arrived before the end of the period of this report. Advantages of the system are high repetition rate (megaHz), high intensity, narrow pulse duration, reliability, and pseudo double beam operation.